Difference Between Acceleration and Retardation

The concept of acceleration is an important one when it comes to study of moving bodies. Acceleration refers to the rate in change of velocity of a moving body. If a body is moving at a constant velocity, there is no change and hence it has no acceleration. You can understand the concept with a moving car. If you are driving a car and moving at a constant speed of 50mph, you are not accelerating, but the moment you start pressing the accelerator and press it further at a constant rate, the car accelerates as its velocity increases at a constant rate. This is known as acceleration. There is another concept linked with acceleration, and known as retardation that people remain confused with. This article will clearly explain the differences between acceleration and retardation to dispel any doubts in the minds of the readers.

If you watch a cycling race, you often see a cyclist zipping past another cyclist. This happens because the faster cyclist is moving at a faster speed than the slower one. But there is more to it than catches your eyes. If the slower cyclist is moving at a constant speed, he has no acceleration. But it is apparent that the one coming from behind is speeding up, he has got a change of velocity that helps him go past the slower one. This rate of change of velocity or change of velocity per unit of time is called acceleration and is explained through Newton’s laws of motion.

If u is the intial velocity and v is the final velocity of the cyclist, acceleration is given by the following equation

V = U + at

Or, a = (V – U)/t

However, there are instances when a fast moving body may be slowing down as when a motorist applies brakes at a traffic light or when a fast moving train halts slowly at a station. Here too there is a change in rate of velocity but in contrast to acceleration, the velocity is decreasing. These conditions are called cases of retardation (or deceleration). Let us see it with an example. When a boy throws up a ball in air, the ball has some initial velocity that gradually reduces until the ball reaches its highest point in the air. This means that this is a case of retardation. On the other hand, when the ball starts its downward journey, it has an initial velocity of zero but it increases gradually under gravity and is maximum just before it strikes the ground. This is a case of acceleration.